Facile and Controllable Preparation of poly(St-co-MMA)/FA Microspheres Used as Ultra-Lightweight Proppants

Hydraulic fracturing is an important technology for the exploitation of unconventional oil or gas reservoirs. In order to increase the production of oil or gas, ultra-lightweight proppants with a high compressive strength are highly desirable in hydraulic fracture systems. In this work, a new type of ultra-lightweight proppant, poly(styrene-co-methyl methacrylate)/fly ash (poly(St-co-MMA)/FA) composites with a high compressive strength were prepared via in situ suspension polymerization. The Fourier transform infrared (IR) and X-ray powder diffraction (XRD) analyses confirmed that the poly(St-co-MMA)/FA composites were successfully prepared. The morphology analysis indicated that the composite microspheres show good sphericity, and FA powder was evenly dispersed in the matrix. The apparent density of the microspheres was between 1 and 1.3 g/cm3, which is suitable for hydraulic fracturing. Furthermore, the compressive strength and thermostability were dramatically improved with the incorporation of FA, which could withstand high pressures and temperatures underground. The obtained poly(St-co-MMA)/FA composite microspheres are promising for application as an ultra-lightweight (ULW) proppant in oil or gas exploitation, which provides a new approach for the design of high performance proppants.

Microwave-assisted oxidative coupling of thiols using polystyrene supported bromoderivatives of 2-oxazolidone

Polymer-supported reagents have become popular in synthetic organic chemistry over the past decades. But the kinetics of polymer-supported reactions is slow compared to solution phase synthesis because of the poor diffusion of the reactants through the macromolecular polymer matrix. This difficulty can be reduced to a great extent by performing polymer-supported reactions under microwave (MW) conditions. The present work is focussed on the design and development of an innovative, powerful, MW stable and recyclable polymeric reagent prepared by attaching bromoderivative of 2-oxazolidone into the macromolecular matrix of polystyrene. 3% cross-linked polystyrene was prepared by free radical aqueous suspension polymerization technique using tetra ethylene glycol diacrylate as the cross-linking agent and the resulting beads were functionalized by chloromethylation followed by reaction with 2-oxazolidone. Bromine functionality is introduced into the polymer by treating with bromine in carbon tetrachloride. The synthetic utility of the prepared polymeric reagent was demonstrated by the oxidative coupling of thiols to disulfides under MW irradiation. No over oxidation was observed in this protocol and the utilization of polystyrene support simplifies work up and product isolation. The synthesised polymeric reagent displayed good cyclic stability up to five cycles without any substantial decrease in bromine content and satisfactory storage stability under normal laboratory condition. Moreover this may be the first report that uses MW energy for the oxidation of thiols to disulfides using polymer-supported reagents. [Formula: see text]

Preparation, Characterization and Properties of some Acrylic Base Latex: A Review

Acrylic polymer latex has versatile role in many academic and industrial applications like paint, adhesives, textile, paper industry, concrete, surface coating, synthetic rubber and many ones. Acrylic base polymer latex can be prepared by various polymerization methods like Batch emulsion, Seeded emulsion, Situ miniemulsion, Atom transfer radical, Free radical copolymerization, Pickering miniemulsion, Semi-continuous seeded emulsion, dispersion copolymerization, aqueous suspension polymerization etc. in different solvents i.e. 1,1,2-trichloroethane, water, deionized water, 1,4-dioxane, chloroform, tetra hydro furan, toluene, benzene, nitric acid and so on. Acrylic latexes possessed various properties such as increased particle size which resist centrifugal nature and reduce viscosity of heavy oil, layered coating on steel improve lustre along with flexibility, tensile strength and thermal stability too. Acrylic latexes increase silicon intensity in silicon nanoparticles by controlling pH of emulsion during polymerization and also super paramagnetic behaviour of Fe2O3 nanocomposites latex controlled by pH. In this connection, many researchers have synthesized various acrylic base polymer latex or its composites, investigate its utility in different forms for different purposes to improve properties as required. In this review our main emphasis is to investigate the synthesis, characterisation and application of various acrylate polymer latexes.

Cellulose Nanofibers/Polycarbonate Nanocomposite

In this study, cellulose nanofiber (CNF) was prepared from carrot residues and further surface modification was carried out using suspension polymerization. Subsequently, these CNFs were added to polycarbonate (PC) to prepare a series CNF reinforced nanocomposites. TEM results show that the average diameter of the fiber after 2,2,6,6-Tetramethylpiperidinyloxy (TEMPO) radical oxidation is 4.46 nm, and the average diameter of the TEMPO oxidized nanofiber modified by suspension polymerization is 7.65 nm, which confirms that the carrot fiber has been successfully prepared into nanoscale. The results of FT-IR analysis show that the lignin and impurities on carrot fibers can be removed effectively after alkali treatment. In addition, the absorption peak of the functional group analyzed by FT-IR also confirmed that the TEMPO radical oxidation and suspension polymerization method were successfully carried out. Contact angle analysis results show that the contact angle of the CNF modified by suspension polymerization method was increased, indicating that the hydrophobicity of the fiber has been significantly improved. Moreover, this will lead to the better compatibility between CNF and PC matrix. Mechanical property analysis also shows that the surface modified CNF has a stronger reinforcing effect on PC than the unmodified one. Furthermore, the results show that the dispersion of CNF in the matrix of nanocomposite prepared by dilution of masterbatch was better than that of the one prepared by directly adding of CNFs. The better dispersion of CNFs in the PC matrix led to the better mechanical properties. The increment of tensile strength of the nanocomposite prepared by dilution of masterbatch can reach to 21.75%. In the analysis of transparency, the transmittance of modified CNF containing nanocomposite was larger than that of unmodified CNF containing one. The transmittance of the nanocomposites containing modified CNFs was larger than 70%, which was close to that of pure PC.

Preparation and Properties of Thermally Expandable Microspheres for Foam Coating

A type of thermally expandable microspheres (TEMs) for foam coating was prepared by suspension polymerization with acrylonitrile (AN), methyl methacrylate (MMA), vinyl acetate (VAC) as shell polymer monomers and i-pentane as core foaming agent. The effects of an aqueous additive (Sodium Chloride, NaCl) on the size and distribution of TEMs, and the effects of crosslinking degree, i-pentane dosage and monomer mass ratio on the expansion property, expansion temperature and solvent-resistance of TEMs were investigated. The results showed that when the dosage of NaCl was close to the saturation solubility (30%), the dosage of crosslinking agent and alkane were about 0.09% and 7.4%, and the mass ratio of AN/MMA/VAC w rm distribution and good solvent resistance, the expansion diameter ratio was 5 times under 110~120 C, which meets the application requirements for foam coating of leather or synthetic leather.

Effect of Pore Size Distribution and Amination on Adsorption Capacities of Polymeric Adsorbents

Polymeric adsorbents with different properties were synthesized via suspension polymerization. Equilibrium and kinetics experiments were then performed to verify the adsorption capacities of the resins for molecules of various sizes. The adsorption of small molecules reached equilibrium more quickly than the adsorption of large molecules. Furthermore, the resins with small pores are easy to lower their adsorption capacities for large molecules because of the pore blockage effect. After amination, the specific surface areas of the resins decreased. The average pore diameter decreased when the resin was modified with either primary or tertiary amines, but the pore diameter increased when the resin was modified with secondary amines. The phenol adsorption capacities of the amine-modified resins were reduced because of the decreased specific area. The amine-modified resins could more efficiently adsorb reactive brilliant blue 4 owing to the presence of polar functional groups.

Poly (Amidehydrazide) Hydrogel Particles for Removal of Cu2+ and Cd2+ Ions from Water

Poly(amidoamine)s (PAMAM) are very effective in the removal of heavy metal ions from water due to their abundant amine and amide functional groups, which have a high binding ability to heavy metal ions. We synthesized a new class of hyperbranched poly(amidehydrazide) (PAMH) hydrogel particles from dihydrazides and N,N′-methylenebisacrylamide (MBA) monomer by using the A2 + B4 polycondensation reaction in an inverse suspension polymerization process. In Cd2+ and Cu2+ ion sorption tests, the synthesized dihydrazide-based PAMH hydrogel particles exhibited sorption capacities of 85 mg/g for copper and 47 mg/g for cadmium. Interestingly, the PAMH showed only a 10% decrease in sorption ability in an acidic condition (pH = 4) compared to the diamine-based hyperbranched PAMAM, which showed a ~90% decrease in sorption ability at pH of 4. In addition, PAMH hydrogel particles remove trace amounts of copper (0.67 ppm) and cadmium (0.5 ppm) in water, below the detection limit.